Method of manufacturing a semiconductor device whereby photomasks comprising partial patterns are projected onto a photoresist layer so as to merge into one another

ABSTRACT

A method of manufacturing a semiconductor device whereby a photoresist layer is provided on a surface of a slice of semiconductor material, after which two photomasks corresponding to adjoining portions of a pattern to be formed in the photoresist are projected on the photoresist by means of a projection lens, with overlapping edges. Strip-shaped transparent end portions of the two photomasks which are situated within this edge and which overlap one another in projection are provided with strip-shaped connection patterns which overlap one another in projection and which exhibit a complementary transmittance in projection. To keep the quantity of computer data necessary for describing the photomasks comparatively small, the strip-shaped transparent end portions of the two photomasks overlapping one another in projection are provided at their edges only with strip-shaped connection patterns overlapping one another in projection.

This is a continuation of application Ser. No. 08/352,408, filed Dec. 8,1994, now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to a method of manufacturing a semiconductordevice whereby a photoresist layer is provided on a surface of a sliceof semiconductor material, after which photomasks corresponding tomutually connecting portions of a pattern to be formed in thephotoresist are projected onto the photoresist by means of a projectionlens, with pattern edges superimposed on one another, while strip-shapedtransparent end portions of the photomasks situated within this edge andmutually overlapping in projection are provided with strip-shapedconnection patterns which overlap one another in projection and whichexhibit a complementary transmittance in projection.

In such a method, a pattern which is too large for being projected bymeans of a single photomask onto a layer of photoresist is subdividedinto mutually adjoining partial patterns which are accommodated indifferent photomasks. These photomasks are projected onto thephotoresist with overlapping edges each time, so that the portions ofthe pattern to be formed merge into one another again in projection.Integrated circuits may thus be manufactured which cover a comparativelylarge surface area of the semiconductor slice. The total pattern in thephotoresist layer is then formed by the transparent end portions whichoverlap in projection and lie inside the edges and by the transparentend portions of the masks which do not overlap in projection and are notsituated within the edges.

EP-A-434142 discloses a method of the kind mentioned in the openingparagraph whereby strip-shaped transparent end portions of thephotomasks overlapping one another in projection are provided over theirentire surface areas with connection patterns having a transmittancewhich shows a gradient seen in the longitudinal direction of thestrip-shaped transparent end portions. This is achieved in that thesestrip-shaped transparent end portions are provided with non-transparentregions whose number and/or size changes in the longitudinal directionof the strip-shaped end portions and which are not imaged individuallyin projection.

Were the photomasks not provided with such connection patterns, then thephotoresist layer would receive a total radiation dose at the area ofthe transparent portions overlapping one another in projection which istwice the radiation dose at the area of transparent portions of thephotomasks not overlapping one another in projection. The transparentportions which overlap in projection would then receive a doubleradiation dose. With photomasks projected on a positive photoresist, apattern will be formed therein after development which shows a greaterwidth where it was irradiated with the double dose compared with whereit was irradiated with the single dose. In the case of projection on anegative photoresist, a pattern with a smaller width is formed by doubleirradiation. Wherever the masks overlap, a widening or narrowing oflines will occur, so that the photomask patterns do not merge seamlesslyinto one another. Since the connection patterns of the photomasks show acomplementary transmittance in projection, it is achieved that thephotoresist layer does receive an equally large total radiation dose atthe areas of strip-shaped transparent portions overlapping one anotherin projection during the projection of the photomasks, compared withareas where transparent portions of the photomasks do not overlap inprojection. The photoresist is accordingly irradiated with exactly thesame radiation dose over the entire surface area of the slice. Thepatterns of the photomasks will thus merge into one another seamlessly,i.e. without widening or narrowing of lines.

A photomask suitable for being projected onto a layer of photoresist bymeans of a projector in practice comprises a glass plate covered with ametal layer, such as chromium, into which a pattern of transparentportions has been etched. An electron beam writes the pattern into aphotoresist layer provided on the metal layer. After development, a maskwill have been formed which is used for etching the metal layer into thedesired pattern. The electron beam is controlled by a computer duringwriting from a computer data file in which the pattern was laid down. Apattern thus provided on a glass plate is projected onto the photoresistlayer in practice by means of a projection lens on a reduced scale, forexample, reduced by a factor three or five.

The computer data files in which the photomasks have been laid down andwhich are used in the known method as described comprise a huge quantityof data necessary for defining the connection patterns. It may benecessary in practice for very many, for example 5000 lines of the masksto merge into one another in projection. This may lead to an undesirablylarge quantity of computer data when the known connection patterns areused.

SUMMARY OF THE INVENTION

The invention has for its object inter alia to improve the methodmentioned in the opening paragraph in such a manner that the patterns ofthe photomasks still merge seamlessly into one another in thephotoresist layer, while nevertheless the quantity of computer datanecessary for laying down the patterns of the photomasks is considerablyreduced.

According to the invention, the method is for this purpose characterizedin that the strip-shaped transparent end portions of the photomasksoverlapping one another in projection are provided at their edges onlywith the strip-shaped connection patterns overlapping one another inprojection. The connection patterns thus occupy a surface area on thephotomask which is only a portion of that which is occupied by theconnection patterns in the known method described above. In the knownmethod, said surface area was equal to the surface area occupied by thetransparent end portions of the photomasks overlapping one another inprojection, in the method according to the invention only a portionthereof. The quantity of computer data necessary for laying down theconnection patterns in the transparent end portions of the photomasksoverlapping one another in projection is thus considerably reduced.

The invention is based on the recognition that said widening ornarrowing of lines results only from the dose with which the photoresistis irradiated at the areas of the edges of the transparent strip-shapedportions which overlap one another in projection. The measure accordingto the invention ensures that the photoresist receives in total anequally large radiation dose at the areas of these edges as at the areasof transparent portions of the photomasks which do not overlap inprojection. No widening of lines accordingly occurs at the areas of theedges. Between said edges, the photoresist does receive a radiation dosewhich is twice as large, but a widening of lines which would be theresult thereof is as it were compensated for within the edges.

Preferably, the strip-shaped transparent end portions of the photomaskswhich overlap one another in projection are provided at their edges withstrip-shaped connection patterns having a width which, upon projectionon the photoresist, is greater than 0.2λ/NA, where λ is equal to thewavelength of the radiation used in the projection, and NA is equal tothe numerical aperture of the projection lens used in the projection.

It is found that the widening of lines discussed above substantiallydoes not occur when connection patterns having such a width are used.With a width of the strip-shaped connection patterns equal to 0.2λ/NA,the widening of lines is only one tenth the widening of lines whichwould occur if the transparent end portions of the two photomasks werenot provided with connection patterns. The widening of lines is evenless when the width is greater than 0.2λ/NA.

The connection patterns are imaged continuously during the projection ofthe photomasks on the photoresist layer when the strip-shaped connectionpatterns overlapping one another in projection comprise transparentregions which are formed as rectangular regions with a length and awidth which are smaller than 0.4λ/NA in projection, where λ is thewavelength of the radiation used in the projection and NA is thenumerical aperture of the projection lens used in the projection.

To limit the quantity of computer data necessary for laying down themasks, the strip-shaped connection patterns overlapping one another inprojection are formed as a single row of rectangular transparentregions.

The quantity of computer data necessary for laying down the photomasksis further limited when the connection patterns overlapping one anotherin projection exhibit a complementary transmittance which remainsconstant over their entire surface in projection. The transmittance ofmutually overlapping connection patterns may be, for example, 30% and70%, respectively. Different sets of computer data are then necessaryfor the masks for describing the connection patterns. This is not thecase when the connection patterns overlapping one another in projectionexhibit a complementary transmittance of 50% over their entire surface.The overlapping connection patterns are identical then, whereby therequired quantity of computer data is limited still further.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below by way of examplewith reference to a drawing, in which:

FIGS. 1 to 4 diagrammatically show a few stages in the manufacture of asemiconductor device, where photomasks comprising partial patterns areprojected continuously on a photoresist layer, FIG. 1 in plan view andFIGS. 2 to 4 in cross-section,

FIGS. 5a, c and d show detail of a number of photomasks, and FIG. 5b isa standardized graph showing the radiation dose D(x) received by thephotoresist on the surface of the slice as a function of the location xon this surface,

FIG. 6 diagrammatically and in plan view shows a relevant stage in themanufacture of a semiconductor device, where photomasks comprisingpartial patterns provided with connection patterns of complementarytransmittance are projected on a photoresist layer so as to merge intoone another, and

FIGS. 7 to 9 diagrammatically show photomasks with partial patternsprovided with preferred embodiments of connection patterns ofcomplementary transmittance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4 diagrammatically show, FIG. 1 in plan view and FIGS. 2 to 4in cross-section, a few stages in the manufacture of a semiconductordevice where a photoresist layer 3 is provided on a surface 1 of a sliceof semiconductor material 2, after which photomasks 4 and 5corresponding to mutually adjoining portions of a pattern 6 to be formedin the photoresist 3, with an edge 7 of the photomask 4 and an edge 8 ofthe photomask 5 overlapping one another as indicated diagrammaticallywith arrows 9, are so projected on the photoresist 3 that strip-shapedtransparent end portions 10 of the photomask 4 situated within the edge7 and strip-shaped transparent end portions 11 of the photomask 5situated within the edge 8 overlap one another in projection. Thepattern 6 is formed in the photoresist 3 through development of thephotoresist 3. This photoresist mask may be used, for example, as animplantation mask. Ions of a dopant are then implanted in the slice 2during an ion implantation step to be carried out, as is indicateddiagrammatically in FIG. 3 with broken lines 14. Doped semiconductorzones 15 are then formed during a subsequent heat treatment.

In FIG. 1, the masks 4 and 5 and the pattern 6 formed in the photoresistlayer 3 are drawn at the same size for reasons of clarity, but inpractice the masks 4 and 5 are projected on the photoresist layer, forexample, reduced by a factor three or five.

In this method, the pattern 6 to be formed is subdivided into mutuallyadjoining partial patterns which are provided in the photomasks 4 and 5.These photomasks 4 and 5 are projected on the photoresist 3 with theiredges 7 and 8 overlapping one another, so that the partial patternsmerge into one another again in projection. Integrated circuits may thusbe manufactured which cover a surface area of the slice of semiconductormaterial on which the desired pattern cannot be imaged by means of asingle photomask. The pattern 6 in the photoresist layer 3 comprisesstrip-shaped portions 16 which are formed by the transparentstrip-shaped end portions 10 and 11 which overlap one another inprojection and are situated within the edges 7 and 8, portions 17 formedby transparent portions 10A of photomask 4 not overlapping with portions11 or 11A of photomask 5 in projection and not situated within the edge7, and portions 18 formed by transparent portions 11A of photomask 5which do not overlap with portions 10 or 10A of photomask 4 inprojection and are not situated within the edge 8.

The photoresist layer 3 receives a total radiation dose at the area ofthe transparent portions 10 and 11 overlapping one another in projectionwhich is twice as great as that received at the area of transparentportions of the photomasks 12 and 13 which do not overlap one another inprojection. The transparent portions 10 and 11 overlapping one anotherin projection receive a double radiation dose. When the photomasks areprojected onto a positive photoresist 3, as in the present example, apattern 6 will be formed therein after development whose strip-shapedportions 16 irradiated with the double dose will have a greater widththan the strip-shaped portions 17 and 18 irradiated with the singledose.

FIG. 5a shows a detail of a photomask 20 with a strip-shaped transparentportion 21 etched into a chromium layer 22 which was provided on a glasssubstrate 23. When this portion of the mask is projected on thephotoresist layer 3 during a certain irradiation time t, the photoresistwill receive a radiation dose D(x) which shows a gradient as indicatedwith line 24 in FIG. 5b in the direction transverse to the projection ofthe strip-shaped portion 21 as a function of the location x on thesurface of the slice. FIG. 5b shows this gradient in a standardizedform. The dose D(x) is 0 in those locations where the photoresistreceives no radiation, and 1 in those locations where the photoresistreceives a maximum radiation dose. The location x on the surface of theslice is given in units λ/NA, λ being the wavelength of the radiationused in the projection and NA is the numerical aperture of theprojection lens used for the projection. The gradient of the radiationdose D(x) shown in this standardized form is valid for each projectionsystem used in practice. For a usual projection system--such as, forexample, a projector of the PAS 2500 (ASM) type--which pictures thephotomasks on the photoresist five times reduced with radiation having awavelength λ of 436 nm and by means of a projection lens with anumerical aperture NA of 0.43, the unit λ/NA is approximately 1000 nm.The radiation dose D(0) is approximately 0.3 on the edge of the mask,where x=0. The irradiation time t is now so chosen in practice that thephotoresist becomes capable of development in those locations where theradiation dose D(x) is greater than 0.3, and is just incapable ofdevelopment in those locations where the radiation dose D(x) is smallerthan 0.3.

When the photoresist is irradiated twice with the same mask 20, thephotoresist is irradiated with a radiation dose D₁ (x) which shows agradient as indicated with line 25 in FIG. 5b. This radiation dose D₁(x) indicated with line 25 is twice the radiation dose D(x) indicatedwith line 24 (D₁ (x)=2.D(x)). It can be derived from FIG. 5b that theradiation dose indicated with line 25 has the value 0.3 for x=-0.075units λ/NA. Upon development, therefore, a wider pattern is formed inthe photoresist in the case of double irradiation than in the case ofsingle irradiation. For the practical projection system mentioned above,this line widening through double irradiation amounts to approximately75 nm.

The line widening described with reference to FIG. 5 was based on apositive photoresist, of which irradiated portions are soluble indeveloper. When a negative photoresist is used, the non-irradiatedportions are soluble in developer. Irradiation with a double dose thenleads to narrowing of lines, not to widening of lines.

A widening or narrowing of lines takes place where the masks overlap inthe method where by photomasks comprising partial patterns are projectedon a photoresist layer so as to adjoin one another. The photomaskpatterns do not merge seamlessly into one another then. When thetransparent end portions 10 and 11 of the photomasks 4 and 5 areprovided with the connection patterns 30 which have a complementarytransmittance in projection, it is achieved that the photoresist layer 3does receive the same radiation dose in total at the area of thestrip-shaped transparent portions 10 and 11 overlapping one another inprojection during the projection of the photomasks 4 and 5 as at theareas of transparent portions 12 and 13 of the photomasks which do notoverlap in projection. The photoresist is thus irradiated with exactlythe same radiation dose over the entire surface of the slice. Thepatterns of the photomasks 4 and 5 will accordingly merge into oneanother seamlessly, so without widening or narrowing of lines.

FIG. 5c shows in detail a portion of a photomask 40 etched into achromium layer 42 which was provided on a glass substrate 43. The maskis provided with a connection pattern 44 which has a width b of 0.1λ/NAin projection on the photoresist and which, for example, has atransmittance of 50% over its entire surface area. When this portion ofthe mask 40 is projected twice on the photoresist layer 3, thephotoresist is irradiated with a radiation dose D₂ (x) which shows agradient as indicated with line 27 in FIG. 5b as a function of thelocation x in the direction transverse to the projection of thestrip-shaped portion 41. This radiation dose D₂ (x) is the sum of theradiation dose indicated with line 24 and the radiation dose indicatedwith line 26 and shifted over a distance 0.1λ/NA: D₂ (x)=D(x)+D(x-b). Itcan be derived from FIG. 5b that the radiation dose D₂ (x) indicatedwith line 27 has the value 0.3 for x=-0.030λ/NA. This widening of theline upon double radiation is approximately 30 nm for the practicalprojection system mentioned above.

FIG. 5a further shows in detail a portion of a photomask 45 etched in achromium layer 47 which was provided on a glass substrate 48. The maskis provided with a connection pattern 49 which has a width 2b of 0.2λ/NAin projection on the photoresist and which has a transmittance of, forexample, 50% over its entire surface area. When this portion of the mask45 is projected twice on the photoresist layer 3, the photoresist isirradiated with a radiation dose D₃ (x) which has a gradient asindicated with line 29 in FIG. 5b as a function of the location x in thedirection transverse to the projection of the strip-shaped portion 46.This radiation dose D₃ (x) is the sum of the radiation dose indicatedwith line 24 and the radiation dose indicated with line 28 and shiftedover a distance 0.2λ/NA: D₃ (x)=D(x)+D(x-2b). It can be derived fromFIG. 5b that the radiation dose D₃ (x) indicated with line 29 has thevalue 0.3 for x<-0.010λ/NA. This line widening upon double irradiationamounts to less than 10 nm for the practical projection system mentionedabove.

The use of the connection patterns 44 and 49 is found to achieve thatthe widening of lines referred to above can be strongly suppressed.Connection patterns were described in the examples which had atransmittance of 50% over the entire surface area. It will be clear thatthe same results are obtained with connection patterns having differenttransmittance gradients over their surface, as long as it is ensuredthat the two connection patterns which overlap one another in projectionhave a complementary transmittance, so that the photoresist receives atotal radiation dose of 0.3 seen over the entire surface area of theconnection patterns.

In the manufacture of the photomasks, the pattern is written into aphotoresist layer provided on the metal layer by means of an electronbeam. A mask is then formed after development which is used for etchingthe metal layer into the desired pattern. The electron beam iscontrolled during writing by a computer from a computer data file inwhich the pattern has been laid down.

To limit the quantity of computer data necessary for laying down thephotomask patterns considerably, according to the invention, thestrip-shaped transparent end portions 10 and 11 of the photomasks 4 and5 overlapping one another in projection are provided at their edges 31only with the strip-shaped connection patterns 30 overlapping oneanother in projection. The connection patterns 30 thus occupy only acomparatively small portion of the surface area of the photomask 4, 5,while their width is greater than 0.2λ/NA in projection on thephotoresist, as described above, λ being the wavelength of the radiationused for the projection and NA being the numerical aperture of theprojection lens used for the projection.

It is found that the widening of lines discussed above substantiallydoes not occur when connection patterns of such a width are used. Whenthe width of the strip-shaped connection patterns is 0.2λ/NA, thewidening of the lines is no more than one tenth the widening of thelines which would occur if the transparent end portions of the twophotomasks were not provided with connection patterns. The widening ofthe lines is even less when the width is greater than 0.2λ/NA.

FIG. 7 shows photomasks 50 and 51 with strip-shaped end portions 52 and53 overlapping one another in projection, with connection patterns 54and 55 having transparent regions 56 and 57 in the form of rectangularregions. These regions have a length and a width smaller than 0.4λ/NA inprojection, λ being the wavelength of the radiation used for theprojection and NA being the numerical aperture of the projection lensused for the projection. These connection patterns 54 and 55 are imagedcontinuously upon projection of the photomasks on the photoresist layer.Furthermore, the size of the regions 56, 57 is so distributed over thesurface of the connection patterns 54 and 55 that the transmittance ofthese connection patterns in projection shows a continuous gradient, asin a usual grey stage. Such rectangular regions can be described bymeans of comparatively few computer data, so that the quantity of datanecessary for describing the photomasks 50 and 51 is limited. Thetransparent end portions 52, 53 on the masks 50 and 51 have a length,for example, of 10 μm and a width of 20 μm, while the connectionpatterns 54 and 55 have a length also of 10 μm and a width of 5 μm. Thetransparent rectangular regions 56 and 57 have dimensions which show agradient of approximately 20 steps from 350 nm×400 nm× down to 150nm×150 nm.

To reduce the quantity of computer data necessary for laying down themasks, the strip-shaped connection patterns overlapping one another inprojection are arranged as a single row of rectangular transparentregions.

FIG. 8 shows photomasks 60 and 61 with strip-shaped end portions 62 and63 overlapping one another in projection, with a length of 10 μm and awidth of 20 μm, and with connection patterns 64 and 65 provided withtransparent regions 66 and 67 in the form of rectangular regions havinga length of 400 nm and a width decreasing gradually in steps from 400 nmdown to 159 nm. Since the number of rectangular transparent regions 66and 67 is limited to a single row of such regions, even less computerdata are necessary for laying down these masks 60 and 61 than for themasks 50 and 51 shown in FIG. 7.

FIG. 9 shows photomasks 70 and 71 with strip-shaped end portions 72 and73 overlapping one another in projection, with a length of 10 μm and awidth of 20 μm, and with connection patterns 74 and 75 provided withtransparent regions 76 and 77 in the form of rectangular regions of 400nm length and with a fixed width. The connection patterns 74 and 75 showa complementary transmittance over their entire surface area.

The transmittance of mutually overlapping connection patterns 74 and 75may be, for example, 30% and 70%, respectively. Different sets ofcomputer data are necessary then for the masks for describing theconnection patterns. This is not the case if, as shown in FIG. 9, theconnection patterns 74 and 75 which overlap one another in projectionshow a complementary transmittance of 50% which remains the same overtheir entire surface area in projection. The overlapping connectionpatterns 74 and 75 are then identical for the photomasks 70 and 71,whereby the quantity of computer data required is still further limited.The approximately 20 transparent rectangular regions 76 and 77 then havea width of approximately 250 nm, and a mutual interspacing also ofapproximately 250 nm.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the steps comprising:providing a photoresist layer on a surface of asemiconductor material; providing a first photomask comprising a firstportion of a pattern to be formed in the photoresist, the first portionhaving an end portion, the end portion projecting in a first directionand having a side establishing the origin of a second directionsubstantially transverse to the first direction, the end portioncomprising a connection pattern of selected dimensions, the connectionpattern being disposed only at the side of the end portion and having aselected transmittance, the connection pattern extending a distance ofat least approximately 0.2λ/NA from the origin in the second direction;providing a second photomask comprising a second portion of the pattern,the second portion having an end portion, the end portion projecting ina first direction and having a side establishing the origin of a seconddirection substantially transverse to the first direction, the endportion comprising a connection pattern of selected dimensions, theconnection pattern being disposed only at the side of the end portionand having a transmittance selected to be complementary to thetransmittance of the connection pattern of the first photomask, theconnection pattern extending a distance of at least approximately0.2λ/NA from the origin in the second direction; irradiating thephotoresist through the first photomask using a predetermined radiationdose sufficient to form in the photoresist not associated with theconnection pattern the first portion of the pattern; irradiating thephotoresist through the second photomask using a predetermined radiationdose sufficient to form in the photoresist not associated with theconnection pattern the second portion of the pattern; and theirradiations through the first and the second photomasks being performedso that the respective connection patterns of said photomaskssubstantially overlap and the photoresist associated therewith receivesa complementary radiation dose, the complementary radiation dose beingsubstantially limited to the area of overlap and, in that area, beingsufficient to permit development of said associated photoresist.
 2. Themethod of claim 1, wherein the providing steps comprise selecting aconnection pattern that extends from the side of the associated endportion to a distance of approximately 0.2λ/NA, that distance beingsubstantially uniform along the length of the connection pattern.
 3. Themethod of claim 1, wherein the providing steps comprise selecting aconnection pattern that extends from the side of the associated endportion to a distance of at least 0.2λ/NA, that distance beingsubstantially uniform along the length of the connection pattern.
 4. Themethod of claim 1, wherein the providing steps comprise selectingconnection patterns that include one or more transparent, rectangularregions having length and width dimensions which are each smaller than0.2λ/NA.
 5. The method of claim 4, wherein the providing steps compriseselecting connection patterns that include a plurality of transparent,rectangular regions arranged in a single row.
 6. The method of claim 5,wherein the providing steps comprise selecting connection patterns thatinclude a plurality of transparent, rectangular regions havingsubstantially uniform dimensions.
 7. The method of claim 5, wherein theproviding steps comprise selecting connection patterns that include aplurality of transparent, rectangular regions, the connection pattern ofone such end portion having regions of gradually increasing dimensionsand the connection pattern of the other such end portion havinggradually decreasing dimensions, associated regions of the connectionpatterns being arranged on the respective photomasks so that, in theirradiation steps, complementary transmittance is achieved.
 8. Themethod of claim 4, wherein the providing steps comprise selectingconnection patterns that include a plurality of transparent, rectangularregions which are located and have dimensions so that each connectionpattern has a substantially uniform transmittance of 50% along thelength thereof.
 9. The method of claim 4, wherein the providing stepscomprise selecting connection patterns that include a plurality oftransparent, rectangular regions which have distributed dimensions andlocations so that, in the irradiation steps, the transmittance of eachconnection pattern comprises a continuous gradient, and the gradientassociated with one such connection pattern is complementary to thegradient associated with the other such connection pattern.
 10. A methodof manufacturing a semiconductor device, the steps comprising:providinga photoresist layer on a surface of a semiconductor material; providinga first photomask comprising a first portion of a pattern to be formedin the photoresist, the first portion having an end portion, the endportion projecting in a first direction and having a side establishingthe origin of a second direction substantially transverse to the firstdirection, the end portion comprising a connection pattern, theconnection pattern being disposed at the side of the end portion so asto extend therefrom in the second direction a distance substantially of0.2λ/NA; providing a second photomask comprising a second portion of thepattern, the second portion having an end portion, the end portionprojecting in a first direction and having a side establishing theorigin of a second direction substantially transverse to the firstdirection, the end portion comprising a connection pattern, theconnection pattern being disposed at the side of the end portion so asto extend therefrom in the second direction a distance substantially of0.2λ/NA; irradiating the photoresist through the first photomask using apredetermined radiation dose sufficient to form in the photoresist notassociated with the connection pattern the first portion of the pattern;and irradiating the photoresist through the second photomask using apredetermined radiation dose sufficient to form in the photoresist notassociated with the connection pattern the second portion of the patternand so that the respective connection patterns thereof substantiallyoverlap and provide in the photoresist associated therewith an aggregatecomplementary radiation dose, the complementary radiation dose beingsubstantially limited to the area of overlap and, in that area, beingsufficient to permit development of said associated photoresist.
 11. Themethod of claim 10, wherein the providing steps comprise selectingconnection patterns having substantially equal lengths.
 12. The methodof claim 10, wherein the providing steps comprise selecting a connectionpattern having a length and that extends a substantially uniformdistance in the second direction from the side of the associated endportion along the entire length of the connection pattern.
 13. Themethod of claim 10, wherein the providing steps comprise selecting aconnection pattern having a length substantially equal to the length ofthe associated end portion.
 14. The method of claim 10, wherein theproviding steps comprise selecting connection patterns that include oneor more transparent, rectangular regions having length and widthdimensions which are each smaller than 0.2λ/NA.
 15. The method of claim14, wherein the providing steps comprise selecting connection patternsthat include a plurality of transparent, rectangular regions arranged ina single row.
 16. The method of claim 15, wherein the providing stepscomprise selecting connection patterns that include a plurality oftransparent, rectangular regions having substantially uniformdimensions.
 17. The method of claim 15, wherein the providing stepscomprise selecting connection patterns that include a plurality oftransparent, rectangular regions, the connection pattern of one such endportion having regions of gradually increasing dimensions and theconnection pattern of the other such end portion having graduallydecreasing dimensions, associated regions of the connection patternsbeing arranged on the respective photomasks so that, in the irradiationsteps, complementary transmittance is achieved.
 18. The method of claim14, wherein the providing steps comprise selecting connection patternsthat include a plurality of transparent, rectangular regions which arelocated and have dimensions so that each connection pattern has asubstantially uniform transmittance of 50% along the length thereof. 19.The method of claim 14, wherein the providing steps comprise selectingconnection patterns that include a plurality of transparent, rectangularregions which have distributed dimensions and locations so that, in theirradiation steps, the transmittance of each connection patterncomprises a continuous gradient, and the gradient associated with onesuch connection pattern is complementary to the gradient associated withthe other such connection pattern.
 20. A method of manufacturing asemiconductor device, the steps comprising:providing a photoresist layeron a surface of a semiconductor material; providing a first photomaskcomprising a first portion of a pattern to be formed in the photoresist,the first portion having an end portion, the end portion comprising aconnection pattern of selected dimensions, the connection pattern beingdisposed only at a side of the end portion and having a selectedtransmittance; providing a second photomask comprising a second portionof the pattern, the second portion having an end portion, the endportion comprising a connection pattern of selected dimensions, theconnection pattern being disposed only at a side of the end portion andhaving a transmittance selected to be complementary to the transmittanceof the connection pattern of the first photomask; the connectionpatterns of the first and second photomasks including one or moretransparent, rectangular regions having length and width dimensionswhich are each smaller than 0.2λ/NA; irradiating the photoresist throughthe first photomask using a standardized radiation dose D ofapproximately 1 so as to form in the photoresist the first portion ofthe pattern; and irradiating the photoresist through the secondphotomask using a standardized radiation dose D of approximately 1 so asto form in the photoresist the second portion of the pattern and so thatthe respective connection patterns substantially overlap and provide inthe photoresist associated therewith a complementary radiation dose. 21.The method of claim 20, wherein the providing steps comprise selectingconnection patterns that include a plurality of transparent, rectangularregions arranged in a single row.
 22. The method of claim 21, whereinthe providing steps comprise selecting connection patterns that includea plurality of transparent, rectangular regions having substantiallyuniform dimensions.
 23. The method of claim 21, wherein the providingsteps comprise selecting connection patterns that include a plurality oftransparent, rectangular regions, the connection pattern of one such endportion having regions of gradually increasing dimensions and theconnection pattern of the other such end portion having graduallydecreasing dimensions, associated regions of the connection patternsbeing arranged on the respective photomasks so that, in the irradiationsteps, complementary transmittance is achieved.
 24. The method of claim20, wherein the providing steps comprise selecting connection patternsthat include a plurality of transparent, rectangular regions which arelocated and have dimensions so that each connection pattern has asubstantially uniform transmittance of 50% along the length thereof. 25.The method of claim 20, wherein the providing steps comprise selectingconnection patterns that include a plurality of transparent, rectangularregions which have distributed dimensions and locations so that, in theirradiation steps, the transmittance of each connection patterncomprises a continuous gradient, and the gradient associated with onesuch connection pattern is complementary to the gradient associated withthe other such connection pattern.